Oriented hollow articles from styrene-acrylonitrile polymer

ABSTRACT

Hollow articles such as bottles are produced from styreneacrylonitrile polymers under orientation conditions to give a high strength product.

United States Patent 1191 Toups 1 Aug. 28, 1973 [54] ORIENTED HOLLOWARTICLES FROM 3,496,258 2/1970 Wiley 224/98 2,745,824 5/1956 Melchore T60/8 .5 R STYRENE ACRYLONITRILE POLYMER 2,739,142 3/1956 Jones et a1.260/8515 HC Inventor: Edward p Bartlesville, OkIa- 2,921,932 1/1960Erbaugh et a1 1. 260 855 R 3,198,775 8/1965 Delacretaz et a]. 260/855 R[73] Asslgnee- Phillips P Cmnpan 3,505,249 4/1970 Skochdopole et a1260/855 11c Battles/me Okla- 3,547,838 12/1970 Moore et a1 260/855 HC[22] Filed: Jan. 14, 1971 [21] Appl. No.: 106,588 Primary Examiner-HarryWong, Jr.

AttorneyYoung & Quigg [52] US. Cl 260/855 R, 260/935 A, 264/98 [51] Int.Cl C08f 15/04, C08f 15/22 58 Field of Search 260/855 R, 85.5 11c, [57]ABSTRACT 260/855; 264/98 Hollow articles such as bottles are producedfrom styrene-acrylonitrile polymers under orientation condi- [56]References Clted tions to give a high strength product.

UNITED STATES PATENTS 3,082,482 3/1963 Gaunt 264/92 8 Claims, N0Drawings ORIENTED HOLLOW ARTICLES FROM STYRENE-ACRYLONITRILE POLYMERBACKGROUND OF THE INVENTION This invention relates to high strengthhollow articles made from styrene-acrylonitrile polymer.

Polystyrene has long been a commercially valuable plastic because of therelatively high tensile strength and exceptional clarity. However, thematerial is also known to the average customer by its tendency to crackor shatter on even light impact. Consequently, many impact grades ofpolystyrene have been produced and efforts have been directed towardincorporation of comonomers to achieve a better balance of properties.Generally, the incorporation of a rubbery component to improve impactstrength results in a serious deterioration of the excellent opticalproperties of polystyrene. Copolymers of styrene and a small amount ofacrylonitrile have achieved substantial commercial success because ofthe fact that such polymers exhibit considerable improvement in impactstrength relative to polystyrene with only a modest deterioration inoptical properties. In addition, styrene-acrylonitrile polymers haverelatively good solvent resistance. However, in applications such asbottles and other hollow articles, properties of styrene-acrylonitrilepolymers are sometimes only marginally acceptable.

Thus, it would be desirable to have hollow articles ofstyrene-acrylonitrile polymer which exhibit further improvement inimpact strength and in some instances optical properties more nearlylike unmodified polystyrene.

SUMMARY OF THE INVENTION It is an object of this invention to providehigh strength hollow articles of styrene-acrylonitrile polymers; it is afurther object of this invention to provide high strength bottles ofstyrene-acrylonitrile polymers; it is yet a further object of thisinvention to provide hollow articles of styrene-acrylonitrile polymershaving improved clarity; and it is still yet a further object of thisinvention to provide high strength hollow articles ofstyrene-acrylonitrile polymers having improved clarlty.

In accordance with this invention, a hollow article is providedcomprising a styrene-acrylonitrile polymer, said article having atensile impact strength of greater than 25 ft-lbs per square inch asmeasured by ASTM D 1822-68, Type S Speciman.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The hollow articles of theinstant invention can be made from any styrene-acrylonitrile copolymer.Such polymers are well known in the art and are generally designated asSAN resins. Generally, these resins will have from to 40 weight percentpolymerized acrylonitrile based on the total weight of polymerizedstyrene and polymerized acrylonitrile, preferred polymers havingapproximately -35 weight percent acryonitrile.

The polymers can contain conventional additives such as fillers,pigments, antioxidants, and the like, and it is also within the scope ofthe invention to utilize a blend of two or more of the above-identifiedpolymers.

The above-identified polymers can be fabricated into the high strengtharticles of the invention by stretching at orientation temperature. Thiscan be done for instance by extruding the polymer into a continuouslength of tubing which is thereafter severed into individual open endparisons and heated, for instance, in an air oven to a temperaturewithin the range of 175-350, preferably 230-320 F. Generally, atemperature of 40-200, preferably -150 F, below the homogeneous melttemperature of the polymer is satisfactory. Thereafter the heatedparison is grasped at each end and stretched longitudinally, pinchedshut at one end, and expanded by means of differential fluid pressureinto conformity with the mold wall to achieve biaxial strengtheningorientation. Apparatus suitable for this fabrication is disclosed inWiley, U.S. Pat. No. 3,288,317, and Turner et al., U.S. Pat. No.3,390,426, the disclosures of which are hereby incorporated byreference. Alternatively a closed end parison can be used which does nothave to be pinched shut.

The high strength hollow articles of the instant invention are ofprimary utility as containers such as bottles although they canconstitute any hollow article requiring high strength and/or highclarity. Resulting articles will have physical properties in typicalwall sections thereof as follows: tensile impact strength in ft-lbs persquare inch as measured by ASTM D 1822-68, Type S Speciman of greaterthan 25, generally about 39.2 or greater in the longitudinal directionand a tensile impact in ft-lbs per square inch as measured by ASTM D1288-68, Type S Speciman in the circumferential direction of greaterthan 30, preferably about 47.2 or greater. The upper limit on the impactstrength can vary greatly depending primarily on the amount ofstretching achieved at orientation temperature. As a general rule,however, the tensile impact in the longitudinal direction will be withinthe range of 25-150 ft-lbs. Generally the tensile impact strength willbe at least about two times the tensile impact strength of a similarwall section of an identical bottle made in accordance with conventionaltechniques utilizing a molten parison. The haze will generally be lessthan 4 percent, preferably about 2.2 or less. Generally the haze will beless than about one-half the haze of the wall section of an identicalbottle made of identical polymer except fabricated in a conventionaltechnique utilizing a molten parison. Of course, samples containingpigments and certain other additives will not exhibit low haze values.

The wall thickness in these typical sections (that is excluding comers,any seal area in the bottom, the thread and neck area, and the like) canvary greatly depending on the application intended for the product, butgenerally will be in the range of 10-50, preferably 15-40, mils.

The longitudinal stretch should be in the range of 40-200, preferably50-150, percent. An increase in the length of the stretched portion ofthe parison from 5 inches to 10 inches, for instance, would be a percentstretch.

EXAMPLE A styrene-acrylonitrile polymer sold under the trade name Tyril867 by Dow Corporaton was extruded into tubing having an outsidediameter of 0.856-inch and a wall thickness of mils. The resultingtubing was passed through a cooling zone utilizing 7885 F cooling waterand cooled to room temperature. It was thereafter cut into 5.25-inchlengths and heated to 259 F over a period of 10 minutes in an air oven.It was then grasped at each end while at this temperature and stretchedlongitudinally 50 percent to give a longitudinal orientation and apolished oz. Boston round mold closed threeabout having a leading edgeat one end thereof which sealed the parison shut at this end. Air at atemperature of 8090 F and a pressure of 70 psia was introduced to expandthe parison out into conformity with the walls of the molds to givecircumferential orientation. The overall cycle time was 12 seconds andthe bottle had a good appearance.

An identical resin was blown into bottles utilizing a conventionalblow-molding technique wherein the melt temperature of the polymer was400 F. Bottles were blown utilizing a polished 10 02. Boston round moldin optimum conditions for conventional blow molding. Overall cycle timewas 22 seconds and the bottle had a good appearance. Physical propertieswere determined on the bottles made in accordance with the invention andthe bottles in the conventional blow molding operation using specimenscut from the side walls of the bottles. The results were as follows:

TABLE I Conventional Properties Invention Bottle Tensile Strength, psi10,890 8,920

(ASTM D 638-68) Elongation, 7 5 (ASTM D 63868) Tensile Modulus, psi249,000 l99,000 (ASTM D 638-68) Tensile, lnpact, ft-Ibs/in Longitudinal39.2 NA Circumferential 47.2 I92 (ASTM D 1822-68 Type S Speciman) Haze,2.2 6.7

reduced almost to the level of pure polystyrene.

While this invention has been described in detail for the purpose ofillustration, it is not to be construed as limited thereby but isintended to cover all changes and modifications within the spirit andscope thereof.

1 claim:

1. A bottle made by extruding a polymer composition comprising as thesole polymeric ingredient a styreneacrylonitrile copolymer having 10 to40 weight percent polymerized acrylonitrile and to 60 weight percentpolymerized styrene into a continuous length of tubing; thereaftersevering said tubing into an individual open end parison and heatingsame to an orientation temperature of 40-200 F below the homogeneousmelt temperature thereof; thereafter stretching said thus heated parisonlongitudinally an amount within the range of 40-200 percent; andexpanding same out into conformity with a mold to give a bottle havingtypical wall sections with a tensile impact strength of greater than 25ft-lbs. per square inch measured in a longitudinal direction.

2. A bottle according to claim 1 wherein said copolymer contains about2035 weight percent polymerized acrylonitrile.

3. A bottle according to claim 1 wherein said wall sections have atensile strength in the circumferential direction of greater than 30ft-lbs per square inch.

4. A bottle according to claim 1 wherein said impact strength inlongitudinal direction is about 39.2 or greater.

5. A bottle according to claim I wherein said wall sections have a hazeof less than 4 percent.

6. A bottle according to claim 1 wherein said wall sections have haze ofabout 2.2 or less.

7. A bottle according to claim 1 wherein said parison is heated to anorientation temperature of 230 to 320 F prior to stretching.

8. A bottle according to claim 1 wherein said wall sections have animpact strength within the range of 25 to ft./lbs. in the longitudinaldirection and a haze of less than 4 percent.

2. A bottle according to claim 1 wherein said copolymer contains about20-35 weight percent polymerized acrylonitrile.
 3. A bottle according toclaim 1 wherein said wall sections have a tensile strength in thecircumferential direction of greater than 30 ft-lbs per square inch. 4.A bottle according to claim 1 wherein said impact strength inlongitudinal direction is about 39.2 or greater.
 5. A bottle accordingto claim 1 wherein said wall sections have a haze of less than 4percent.
 6. A bottle according to claim 1 wherein said wall sectionshave haze of about 2.2 or less.
 7. A bottle according to claim 1 whereinsaid parison is heated to an orientation temperature of 230* to 320* Fprior to stretching.
 8. A bottle according to claim 1 wherein said wallsections have an impact strength within the range of 25 to 150 ft./lbs.in the longitudinal direction and a haze of less than 4 percent.